Journal Article

Seasonal variations of gas exchange and water relations in deciduous and evergreen trees in monsoonal dry forests of Thailand

Atsushi Ishida, Hisanori Harayama, Kenichi Yazaki, Phanumard Ladpala, Amornrat Sasrisang, Kanokwan Kaewpakasit, Samreong Panuthai, Duriya Staporn, Takahisa Maeda, Minoru Gamo, Sapit Diloksumpun, Ladawan Puangchit and Moriyoshi Ishizuka

in Tree Physiology

Volume 30, issue 8, pages 935-945
Published in print August 2010 | ISSN: 0829-318X
Published online June 2010 | e-ISSN: 1758-4469 | DOI:
Seasonal variations of gas exchange and water relations in deciduous and evergreen trees in monsoonal dry forests of Thailand

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This study compared leaf gas exchange, leaf hydraulic conductance, twig hydraulic conductivity and leaf osmotic potential at full turgor between two drought-deciduous trees, Vitex peduncularis Wall. and Xylia xylocarpa (Roxb.) W. Theob., and two evergreen trees, Hopea ferrea Lanessan and Syzygium cumini (L.) Skeels, at the uppermost canopies in tropical dry forests in Thailand. The aims were to examine (i) whether leaf and twig hydraulic properties differ in relation to leaf phenology and (ii) whether xylem cavitation is a determinant of leaf shedding during the dry season. The variations in almost all hydraulic traits were more dependent on species than on leaf phenology. Evergreen Hopea exhibited the lowest leaf-area-specific twig hydraulic conductivity (leaf-area-specific Ktwig), lamina hydraulic conductance (Klamina) and leaf osmotic potential at full turgor (Ψo) among species, whereas evergreen Syzygium exhibited the highest leaf-area-specific Ktwig, Klamina and Ψo. Deciduous Xylia had the highest sapwood-area-specific Ktwig, along with the lowest Huber value (sapwood area/leaf area). More negative osmotic Ψo and leaf osmotic adjustment during the dry season were found in deciduous Vitex and evergreen Hopea, accompanied by low sapwood-area-specific Ktwig. Regarding seasonal changes in hydraulics, no remarkable decrease in Klamina and Ktwig was found during the dry season in any species. Results suggest that leaf shedding during the dry season is not always associated with extensive xylem cavitation.

Keywords: cryo-SEM; drought; embolism; leaf abscission; phenology; water relations

Journal Article.  6262 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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